Question

A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:

• A. 1 km/hr
• B. 1.5 km/hr
• C. 2 km/hr
• D. 2.5 km/hr

Answer 1

The correct option is A 1 km/hr

Suppose he move 4 km downstream in x hours. Then,
Speed downstream $=\left(\frac{4}{x}\right)$ km/hr
Speed upstream $=\left(\frac{3}{x}\right)$ km/hr
$\therefore \frac{48}{\left(4/x\right)}+\frac{48}{\left(3/x\right)}=14$ or $x=\frac{1}{2}$
So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.
Rate of the stream $=\frac{1}{2}(8-6)km/hr=1km/hr$